The present invention relates generally to Photonic Integrated Circuits (PICs) and methods for making the same.
The use of Photonic Integrated Circuits (PICs) including III-V semiconductor compound photonic components or devices is desirable. Such circuits may be monolithic in nature. One example of such a PIC may take the form of an optical crossconnect including a large number of channel counts.
Coupling between active and passive components represents a fundamental difficulty to be overcome in integrating guided-wave photonic devices into PICs. Active components are those that generally require the bandgap of the operational material be close to the photon energy, such as a laser diode, a semiconductor optical amplifier (SOA) or an electroabsorption modulator, for example. Passive components generally exhibit a bandgap energy of an operational material to be substantially higher than a propagating photon, and may take the form of a waveguide based connector, splitter, coupler, optoelectronic switch or wavelength filtering element or wavelength selective element, such as a demultiplexer, for example.
Integration of active and passive components generally requires use of different materials. However, because of stringent lattice matching requirements for crystalline materials, integration of heterogeneous materials with different optical properties may be difficult.
Existing approaches to integrating active and passive components are believed to generally not be effective, leading to poor coupling and high losses, for example. As a result, efforts in integrating a large number of optoelectronic functions on a single chip may be problematic, particularly in telecommunications devices, for example.
Two general approaches include butt coupling and directional coupling. In butt coupling, the waveguide core stack may be selectively removed using chemical etching for example. An aligned passive waveguide structure may then be regrown. Drawbacks of such joints include the use of the growth step, in addition to difficulties associated with reproducing joint geometries, for example. Alternatively, a largely continuous passive waveguide structure having an active layer formed thereon may be used. The active layer may be selectively etched away in those portions intended to be passive.
Alternatively, a selective area growth (SAG) process leveraging differences in growth rates and masks may be used.
In vertical directional coupling, coupling between different epitaxial layers in the vertical plane serving as distinct waveguides may be utilized. Nonetheless, it is believed that each of these methods exhibits shortcomings. For example, the use of epitaxial growth in a manufacturing process limits choices of suitable materials. Losses at coupling points, such as butt joint interfaces, are typically significant, on the order of approximately 2-3 dB/interface for example. Further, typically realized poor manufacturing yields, that may be on the order of about 20%, also lead to high costs associated with these techniques.
Accordingly, it is highly desirable to provide PICs including active and passive devices and methods for making for them.
A photonic integrated circuit including: at least one photonic component being suitable for operation with a plurality of photons and including an operational material having a bandgap energy close to the energy of the photons; and, at least one photonic component being suitable for operation with the plurality of photons, including an operational material having a bandgap energy substantially higher than the photons and being adjacent to the at least one photonic component including an operational material having a bandgap energy close to the energy of the photons; wherein, the at least one photonic component including an operational material having a bandgap energy substantially higher than the photons includes at least one amorphous silicon based alloy material.